Custom entities do not transfer to realms

I uploaded my world with custom entities on it to a realm, when I joined the realm, none of the custom entities transferred, however the vanilla mob resource and behavior packs worked just fine. The packs use version 1.8 and i have changed the UUID's multiple times.

Steps to reproduce:

1. Create a world with a custom entity addon (I use MCPEDL.com)
2. Make sure the entity works on a normal world (Use Experimental gameplay)
3. Upload the world to a Realm.
4. Check to see if the custom entity can be spawned.